Hey everyone,
I'm currently rebuilding the engine on a 1976 914 2.0. It has the original detuned GC coded engine that came with California emissions D-jet, air pump and catalytic converter.

My goal is to keep the engine fairly original while doing any worthwhile upgrades in the process. I would like to keep the D-jet fuel injection if possible but I don't mind ditching the air pump and cat as I don't live in a state that has strict emissions laws.

I'm guessing that the original detuned california D-jet setup is going to be useless with the big bore pistons/upgraded cam profile, is this correct? If so can I retrofit the computer from a U.S. 1973 spec/ROW/euro spec computer with my system? How much of the cali emissions 75-76 F.I. components jive with the earlier systems? I'm already planning to buy a new D-jet wiring harness and I don't mind tuning a system to work properly (as close to "properly" as I can get with a 41 year old analog computer running an engine it wasn't designed to run)
Any advice is appreciated and thanks in advance!

I run the same Raby cam with 96mm pistons, stock stroke, stock L-Jet (vs D-Jet) and it works perfect. This cam has been developed to work with the stock FI system and mild cc increases. Just put a half decent exhaust on the car to make it work properly. My car went from 86 to 112 HP at the crank with these mods.

You can do that with the D-jet as well....same mods apply. The D-jet is not California specific.

The distributor curve is California specific and of course the compression is California specific. Simply get rid of the smog pump as noted... bring it back up to normal 2.0L D-jet compression (or better)....use a D-jet distributor that is not California timing curve....something like the 022 905 205P and corresponding advance unit and the 9590 cam and a good exhaust. Use a better coil and get rid of the points.

The D-jet while harder to adjust than L-jet...IS more adjustable than L-jet by far. Yes....you can get that same average 110-115 hp as L-jet but with better throttle response. Point being that with either system its a great combo. Ray

The LAST thing you want is spark plug inserts, you want 12mm or even 10mm plugs.
The extra meat greatly reduced the cracks forming.
Plug inserts (even assuming they stay in) use a much larger hole, so far more likely to have cracked heads.

Fixing properly involves welding, which requires new seats/machining etc, but that is normal, and bigger valves are "free" at that point. (porting costs extra, pay the man)

The "oversize" inserts are bad, but I suppose a nice stepped silicon bronze insert might work as an effective plug size and crack reducer, but haven't tried that. Yet. (worth lookin at, Ray?)

Plan on at least a new Djet wiring harness (they exist, far better than factory quality even when new)

...but don't ignore the possibility of a fully programmable engine management system.
It can cost about the same, or even less... than a new Djet TPS.

You can probably go MS3+MS3X and fully sequential with LS2 coils for what that Djet harness and a few new DJet parts cost, you can get lots of help tuning it, and the sensors etc can be had at any auto parts store.

If you manage to blow up the ECU, numerous places fix them, if you cannot DIY. (full schematics etc available, and no oddball/obsolete electronic parts)

The factory manifolds etc work great, but you would probably want to use modern injectors... They can be had in the original (or compatible with the hold downs/manifolds) form factor. The ones used from the factory were ~generation one designs, and probably junk after 45 years.

MS2 or MS3 has excellent diagnostics and datalogging... and full schematics and firmware code is available if you are into that.
The fuel maps can be automatically tuned via a wideband O2 and a registered version of Tuner Studio. (works very well with a simple delay table that depends mostly on your exhaust system length)

Of course there is now the Arduino-based setup... Speeduino IIRC.. $180 for a full up assembled ECU, 4 cylinder fully sequential spark and fuel, and GPL firmware all in C.(as well as hardware, fully Open Source) It uses Tuner Studio as well, and can thus also have fuel tables autotuned.
Thats a ~new project but it seems to have no shortage of developers, and there seem to be quite a few running setups.

You could probably stuff that in the original DJet ECU case.

I, for one, regularly embrace our new robot overlords, as I am the guy fixing the robots...

Its copper plated. I have installed a few since then and there are some issues that have to be addressed to make these work properly. When that is done...they are bulletproof.

1. You need to buy the full tool kit on these inserts. The original bunged up spark plug threads MUST be drilled straight and chatter free so that the insert outer cuff pilot cutter guides straight and chatter free. A good drill press or mill is mandatory.

2. You need to buy a couple of blocks of aluminum on your first go around....and a couple of spare inserts. You need to test drill with the seat pilot cutter after you drill the hole so you can be EXACTLY sure you know how much the seat cutter needs to cut to make an exact fit on the insert outer lip so that the cuff does not protrude at all on the outside...and prevent the sealing washer on the spark plug from sealing. This is also critical because the outer cuff or seat is what the insert installation tool partly leverages against when it is deforming the last inner thread to "swage" the insert in.

ALSO...and this is important. Try not to allow the seat cutter to lower that well or deck around the spark plugs on type 4 heads. You really only want to cut the bevel for the sealing cuff on the insert. If you cut too deep...the insert will protrude too far into the chamber...and you will have to grind too much off the inner end of the insert to make sure it does not have the issues I list below. If you have to grind too much off...you may not have enough locking threads left on the inside.

3. You will notice the outer cuff (spark plug end of the insert)...has a very specific bevel to it. from the last comment you need to make sure that the bevel cutter completes enough depth in the head.

4. You need to carefully...with a spark plug or bolt...not the installation tool yet...screw an insert into the finished, tapped and beveled hole...to make sure of two things
A. The insert does not protrude into the combustion chamber past the thread hole. If it does....when the installation tool "swages"/expands the last thread...which is what keeps the insert from backing out of the bore....that last thread will be expanding against "air"...and this allows the insert to twist outward...unseating it and eventually stripping it out.
B. The Threaded insert...must be tested with a spark plug installed in it...using and old plug with a pre-crushed washer... before you install the insert. What you are looking to see...is if the threaded insert is longer by any amount than the actual length of the thread on the plug.
If it is....that empty thread recess will fill with carbon...lock/jam the plug to the insert and result in twisting the insert out of the head.

You will need to grind or file the insert to correct length on the inner end only.

The inner end has several threads that are made...not fully formed. When the installation tool hits these...it "cold rolls" them to expand the insert outward...locking it to the head...while finish forming the inside threads.
Its good that the inserts have several threads. Because of this you can grind off a thread or a thread and a half to set exact length so that there is no overhand of the insert out of the thread bore (to insure locking action)...or over the threads of the spark plug itself to fill with carbon.

I have seen so many of these IMPROPERLY installed...and its why they fail. If all of this is properly set up....these inserts will NEVER fail.

It is not a quickly stripped spark plug fix. In my opinion...this is NOT and "over the fender" repair as they list on their website...but it is a VERY good repair tool. Installing a pair of these on a head that is on the work bench can suck up half a day. Its also possible depending on spark plug angle...that to get the driver insert to go all the way through without digging into the combustion chamber...that you may need to grind the end of the insert tool to length...making it head specific now.

You will also need to measure from the crushed washer of an old plug...to the exact length of the thread of the sparkplug you use....to make sure you buy the correct inserts. Do not just go by suggested part #. Ray